Femoral Torsion Measurement Using MRI with T1 VIBE Dixon Compared with Matched CT of Adult Femoroacetabular Impingement Patients

 

Purpose or Learning Objective: Femoroacetabular Impingement (FAI) is a known cause of hip pain in young patients. Femoral version (FV) is associated with extra-articular hip impingement. Measurement of FV with magnetic resonance imaging (MRI) is controversial. Knee bolstering is commonly used for MRI. We compared MRI- and computed tomography (CT)-based measurements of FV and asked this question: What is the reliability in terms of mean difference and correlation with and without bolstering, and also between two readers?

Methods or Background: A retrospective comparative radiologic study approved by the institutional review board involving a total of 100 hips was performed. Of them, 52 hips (46 patients) underwent standard MRI with knee bolstering; 48 hips had no knee bolstering and an additional MRI sequence. All patients (100 hips) had symptomatic FAI (mean age: 28 ± 10 years). All patients underwent pelvic CT and MRI of the same hip joint (2016–2019). Mean interval between CT and MRI was 20 days. In addition to the routine unilateral multiplanar protocol for chondrolabral lesions, bilateral fast T1 volumetric interpolated breath-hold examination (VIBE) Dixon of the pelvis and of the knee was acquired for 48 hips without bolstering to measure FV. Two readers independently measured FV on both CT and MRI in two separate sessions (Murphy method).

Results or Findings: (1) Mean absolute difference between MRI with bolstering and CT-based measurements of FV of 52 hips was 6.0 degrees ± 3 (− 10 to 7) for reader 1 and 8.4 degrees ± 5 (− 21 to 12) for reader 2. Mean absolute difference between MRI without bolstering and CT-based measurements of FV of 48 hips decreased to 1.3 degrees ± 0.8 (0.2–3.0) for reader 1 and 2.3 ± 1.9 degrees (0–10) for reader 2. Correlation of FV between MRI without bolstering and CT-based measurements was r = 0.993 (p < 0.001) for reader 1 and r = 0.975 (p < 0.001) for reader 2. (2) Mean absolute difference of CT-based measurements of FV between two readers was 2.9 degrees ± 2 (− 0 to 8), and correlation was r = 0.969 (p < 0.001). Mean difference of MRI-based measurements without bolstering of FV between two readers was 3.3 degrees ± 3 (0–10), and correlation was r = 0.943 (p < 0.001).

Conclusion: MRI-based measurement of FV is as accurate and reliable as CT-based measurements when using T1 VIBE Dixon and in patients with FAI. No bolstering during MRI decreased measurement errors in FV, leading to fewer misdiagnoses of FV.

Publication History

Article published online:
02 June 2022

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